1. Field of the Invention
The present invention relates generally to color filters and method for manufacturing the same, and more particularly, to color filters and method for manufacturing the same for liquid crystal display devices.
2. Prior Art
Liquid crystal display (LCD) devices, especially color LCD devices have many applications. For example, the color LCD devices are applicable in laptop computers, DVD players, cellular phones, personal digital assistants (PDA), etc. In order to make an LCD display colorful, a color filter is needed.
FIG. 1 illustrates a conventional color filter 100, which comprises a substrate 101, a black matrix (BM) 102, a red, green and blue color filter layer 103a, 103b and 103c, a protection layer 104, and a transparent conductive layer 105.
Methods for manufacturing the color filter 100 include pigment dispersion method, dyeing method, printing method and electrodeposition method. Regardless of which of the above methods is employed, a black matrix (BM) should be formed on a substrate before further processing for preventing leakage of light due to liquid crystal alignment defects.
Conventionally, a black matrix is formed on a glass substrate by photolithography. The black matrix is generally comprised of a thin metal film, such as a chromium film, with a fine pattern. The black matrix is formed by first sputtering a thin metal film on a substrate in a vacuum environment. Then, a photoresist is applied on the thin metal film. A pattern is formed on the photoresist for defining the pattern of the thin metal film. The thin metal film is then etched in accordance with the pattern formed on the photoresist. The desired black matrix is thus formed after depleting the photoresist on the thin metal film. This photolithography method requires many processing steps, resulting in a higher production cost.
Another conventional method for forming a black matrix is disclosed by Keijiro Inoue, et al. in U.S. Pat. No. 5,786,042, which is entitled “Resin Black Matrix for Liquid Crystal Display Device”. However, the formation of a resin black matrix on a substrate still requires photolithography processes. In addition, the resin black matrix is approximately 1 μm or more in thickness, which reduces the flatness of a color filter.